Light-sensitive photographic elements containing developing agent precursors



United States Patent 3,295 978 LIGHT-SENSITKVE PHOTbGRAPHIC ELEMENTS CONTAINING DEVELOPING AGENT PRE- CURSORS Charles R. Barr, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N0 Drawing. Filed Oct. 2?, 1962, Ser. No. 233,936 7 Claims. (Cl. 96-76) This invention relates to light-sensitive photographic silver halide emulsions and more particularly to photographic silver halide emulsions which contain a photographically compatible precursor of a silver halide developing agent.

It is known to incorporate certain silver halide developing agents in photographic silver halide emulsion layers. Such emulsions are developed after light exposure, by treating them in alkaline solutions which may or may not contain a developing agent. Following development, the developed silver image is fixed by treating the developed silver halide layer in a conventional sodium thiosulfate fixing bath. The developed and fixed photographic emulsion layer is then washed and dried.

Light-sensitive silver halide emulsion layers containing silver halide developing agent tend to have less stability on storage than is desired.

It is therefore an object of my invention to provide silver halide developing agent precursors which can be incorporated with light-sensitive silver halide and because of their stability are photographically compatible until the coating containing them is treated with an activating solution that causes a release of a developing agent from the precursor and provides a pH that is high enough to cause the developing agent to reduce photographically exposed silver halide to silver.

Another object is to provide light-sensitive photographic silver halide emulsions containing the reaction products of certain metals and certain catechols and certain hydroquinones as developing agent precursors which are photographically compatible in the presence of silver halide until the coating containing the emulsion is activated in such a way that an active developing agent is released from the developing agent precursor.

It is a further object of my invention to provide self developing silver halide emulsions in which the developing agents are provided entirely from one of my developing agent precursors.

Still another object is to provide light-sensitive photographic silver halide emulsions containing my developing agent precursors which have stability upon prolonged storage that is equivalent to that of light-sensitive photographic silver halide emulsions without any incorporated developing agents.

Still further objects will become evident from the following specification and claims.

These and other objects are accomplished according to my invention by incorporating as developing agent precursors the photographically compatible, stable reaction products of certain metals and certain developing agents in light-sensitive hydrophilic colloid silver halide emulsion layers or alternatively in a hydrophilic colloid layer either over or under the light-sensitive layer. The compounds useful according to my invention as developing agent precursors include the reaction products of a catechol or a hydroquinone with any metal, which prodnets are photographically compatible at the emulsion coating pH and which can be converted to the free developing agent by an activating solution containing any anion capable of reacting with-the metal ion from the developing agent precursor to form a product which is less dissociated than the developing agent precursor, thus reducing the metal ion concentration below that required by the developing agent precursor. By a photographically compatible developing agent precursor I mean any such precursor which when incorporated into or contiguous to a light-sensitive silver halide emulsion, is either completely inert or is active in such a way as to provide a desirable eifect, for example, a speed increase, antifoggant activity, desirable contrast changes, etc. Metals that are useful in my precursors include beryllium, magnesium, calcium, strontium, barium, scandium, ytterbium, lanthanides, actinides, titanium, zirconium, hafnium, vanadium, columbium, tantalum, chromium, molybdenum, tungsten, manganese, tellurium, rhodium, iron, ruthenium, osmium, cobalt, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, mercury, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, arsenic, antimony, and bismuth.

The preferred developing agent precursors of my invention include those represented by the following formula:

in which M represents metal atoms, such as lead, calcium, cadmium, barium, nickel, zinc, cobalt, antimony, titanium,

- chromium, manganese, palladium, silver, gold, etc., D

represents a silver halide developing agent, such as a catechol developer (e.g., catechol, and substituted catechols that are water soluble and active silver halide developing agents) and a hydroquinone (e.g., hydroquinone and substituted hydroquinones that are water soluble and active silver halide developing agents), and n represents the integer l, 2 or 3.

Usually colorless developing agent precursors are preferred since they can be used in the light-sensitive layers or over light-sensitive layers without causing photographic speed loss by absorbing actinic light. Colored developing agent precursors may be used in emulsion layers under the light-sensitive layers or in certain instances it may be preferred to use them in a layer over the light-sensitive layer for a light filter providing their color is appropriate.

Included among the water soluble and active silver halide developing agents that are reacted with metal salts to form the developing agent precursors of my invention are those represented by the formulas;

(11 11a: Il a R --0 II it 0 H and no -o1r wherein X represents a group, such as a hydroxyl group, an amino group, e.g. a primary amino group, an N-ethylamino group, an N,N-diethylamino group, an N-propylamino group, a hydroxyethylamino group, a sulfopropylamino group, a carboxyethylamino group, a di(hydroxyethyl)amino group, etc., an aminoalkyl group, such as an aminoethyl group, a methylaminoethyl group, a dimethylaminoethyl group, a hydroxyethylaminoethyl group, a carboxyethylaminoethyl group, etc., which can form chelates with the metal atoms in the developing agent precursors; R, R R R R R and R may each represent hydrogen atom, a hydroxyl group, an alkyl group, such as methyl, phenylmethyl, ethyl, propyl, butyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, carboxymethyl, carboxyethyl,

, J sulfopropyl, aminomethyl, B-aminoethyl, 'y-aminopropyI, methylaminomethyl, ethylaminomethyl, propylaminomethyl, ,8-hydroxyethylaminomethyl, fl-hydroxyethylaminoethyl, N,N-dimethylaminoethyl, N-ethyl-N-methylaminoethyl, carboxyethylaminoethyl, etc., an aryl group, such as phenyl, etc., an amino group, e.g., a primary amino group, an N-ethylamino group, an N-ethyl-N-methylamino group, an N,N-dimethylamino group, an N,N-diethylamino group, a carboxyethylamino group, a sulfoethylamino group, a hydroxyethylamino group, etc., such that the groups R, R R and R combined have no more than a total of eight carbon atoms per molecule of developer and such that the groups X, R R and R combined have no more than a total of eight carbon atoms per molecule of developer.

The exact structure of the metal salts of these developers comprising my developing agent precursors is not known with certainty, however it is believed that they probably have the following structures: 1

- R3 R2 Re e I I l l MO R and M O- -OH O R R4 1 L n H 11 wherein X, R, R R R R R R M, and n are as defined previously.

Included among the typical developing agent precursors of my invention are the following compounds:

My light-sensitive photographic silver halide emulsions are of the developing out type and contain in addition to one or more of my developing agent precursors, a silver halide, such as silver bromide, silver chloride, silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide, silver chlorobromoiodide, etc. Alternatively, the developing agent precursors can be incorporated in a layer either over or under the silver halide layer.

My developing agent precursors release from 1 to 3 molecules of developing agent per molecule of precursor depending upon the valence of the metal in the precursor. Usually an amount of the developing agent precursor is incorporated which will provide at least one mole of developing agent per mole of silver halide. However, it may be advantageous to use larger proportions of the precursor when desired.

Any of the hydrophilic colloid carriers used in making photographic silver halide emulsions are used to advantage as carriers for the silver halide(s) and developing agent precursor(s) used in making my photographic ele ments. These hydrophilic colloid carriers include gelatin and gelatin substitutes, such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound. Some colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in U.S. Patent 2,286,215, of Lowe; a far hydrolyzed cellulose ester, such as cellulose acetate hydrolyzed to an acetyl content of 19-26% as described in U.S. Patent 2,327,808 of Lowe and Clark, a water-soluble ethanolamine cellulose acetate as described in U.S. Patent 2,322,- 085 of Yutzy; a polyacrylamide having a combined acrylamide content of 30-60% and a specific viscosity of 0.25- 1.5 on an imidized polyacrylamide of like acrylamide content and viscosity as described in U.S. Patent 2,541,474 of Lowe, Minsk and Kenyon; zein as described in U.S. Patent 2,563,791 of Lowe; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in U.S. Patent 2,768,154 of Unruh and Smith, or containing cyano-acetyl groups, such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in U.S. Patent 2,808,- 331 of Unruh, Smith and Priest; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in U.S. Patent 2,852,382 of Illingsworth, Dann and Gates.

The emulsions used in the photographic element of my invention can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in Sheppard U.S.- Patent 1,574,- 944; Sheppard and Punnett U.S. Patent 1,623,499; and Sheppard and Brigham U.S. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals, such as ruthenium, rhodium, palladium, iridium and platinum. Representative compounds are ammonium chloropalladate, potassium chlor-oplat inate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trive'lli U.S. Patent-2,448,060 and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller, Collins and Dodd U.S. Patent 2,399,083 or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856 and Yutzy and Leermakers U.S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium au-rithiocytanate, potassium chloroaura-te, auric trichloride and 2-aurosu1- fobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents, such as stannous salts (Carroll U.S. Patent 2,487,850), polyamine-s, such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), or bis(B-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions can also be optically sensitized with cyanine and lmerocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301; 1,846,302; and 1,942,- 854; White U.S. Patent 1,990,507; Brooker and White U.S. Patents 2,112,140; 2,165,338; 2,493,747; and 2,739,- 964; Brooker and Keyes U.S. Patent 2,493,748; Sprague U.S. Patents 2,503,776 and 2,519,001; Heseltine and Brooker U.S. Patent 2,666,761; Heseltine U.S. Patent 2,734,900; Van Lare U.S. Patent 2,739,149; and Kodak Limited, British 450,958.

The emulsions may also contain speed-increasing compounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623; Carroll and Allen U.S. Patent 2,288,226; and Carroll and Spence U.S. Patent 2,334,- 864; and the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162.

Photographic emulsions of my invention may be coated on any of the support materials used in photography made of materials, such as glass, the cellulose esters, the

polycarbonates, paper, etc.

Light-sensitive photographic elements containing my developing agent precursors are developed after image exposure by treating the element with an activator solution containing an anion, such as 80 CNS, Cl, Br, I, OH", PO CO etc., which is capable of forming a less dissociated compound than the precursor with the metal ions from the precursor, and which solution has a pH high enough to activate the developing agent freed from the precursor. The pH required may be as low as 5 when the developing agent is 2,5-dihydroxy hydroquinone, but usually for other developers a pH above 8 is required. The activator solution can be made alkaline with any of the alkali metal carbonates, such as sodium or potassium carbonate, etc., and alkali metal hydroxide, such as sodium or potassium hydroxide, etc., an organic amine, such as isopropylamine, n-propylamine, triethylamine, triethanolamine, die-thanolamine, etc.

My invention is still further illustrated by the following typical examples of photographic silver halide elements containing my developing agent precursors.

Example 1 A mixture of 2.4 g. of lead catechol, Compound 1, in 140 ml. of 5% gel, ml. of 7.5% sa-ponin solution and 12 ml. of 2.5% Alkanol B (a propylated naphthalene sulfonate) solution was intimately blended in a colloid mill. To 81 ml. of this suspension was added 12 ml. of a gel-atino silver halide emulsion (containing 0.005 mole of silver) with stirring. This emulsion was coated on a photographic film support at a wet thickness of 0.006 inch. After drying, portions of the photographic element were exposed to a light image. One portion of the exposed element was treated by immersing it for four minutes in a sodium carbonate solution having a pH of 11. Another portion of the exposed element was treated by contacting it with a gel pad containing the above sodium carbonate solution. No development occurred. Other portions of the image exposed element were treated in the same way with sodium carbonate solutions having a pH of 12 and 13.5. In each instance (that is, with immersion in the solution, or by treatment with a gel pad soaked in the solution) development was complete with the solution having a pH of 13.5 but no development occurred from treatment with the solution at a pH of 12.

Example 2 A photographic element was made as in Example 1 but using the lead salt of 2,5-b is[N,N-di(,B-hydroxyethyl) aminomethyl1-hydroquinone in place of lead catechol. This element was exposed to a light image and samples of the exposed element were given the same treatment as given in Example 1. The sodium carbonate solution hav ing a pH of about 11 caused image development.

Similarly, the other developing agent precursors of my invention are used to advantage in photographic elements made as in Example 1. These elements all demonstrate stability comparable to elements containing no developing agent precursor upon storage for prolonged periods of time. Latent images in these elements are readily developed to good silver images upon treatment with an appropriate activator solution.

Photographic elements are made by coating the suspensoin of my developing agent precursor made as in Example 1 but containing no silver halide emulsion as a layer on a support either over or under a layer of the hydrophilic colloid silver halide emulsion. Such elements are developed after image exposure by treatment with a suitable activator solution.

In general, my developing agent precursors are prepared by reacting the developing agent with a watersoluble salt of the metal in which the metal is represented by M as defined previously. This reaction is carried out advantageously in aqueous solution and in the presence of a proton acceptor, such as aminoethanol or other water-soluble amine. The developing agent precursors that are water-insoluble or have limited water solubility are readily separated by filtration and purified by washing with appropriate solvents. The developing agent precursors that are water soluble are concentrated in the reaction mixture by evaporation of water under reduced pressure followed by purification using appropriate solvents.

My invention is still further illustrated by a more detailed description of the preparation of typical developing agent precursors.

Example 3 Compound 1, lea-d catechol, was prepared as follows. To a solution of 11 g. of catechol and 6 ml. of aminoethanol in 200 ml. of water was added a solution of 38 g. of lead acetate in 200 ml. of water with stirrring, whereupon a white solid separated. The resultant mixture was stirred at room temperature for four hours, the solid filtered ofi, washed five times with 50 ml. portions of water, washed two times with 25 ml. portions of ethyl alcohol, and air dried. The yield of white pro-duct was 27 g. This dry solid was ball milled to reduce the particle size sufficiently for incorporation in the emulsion coatlngs.

The other compounds used to illustrate my invention were prepared by similar procedures.

The metal salt complexes of developing agents of my invention are valuable developing agent precursors for incorporation in photo-graphic silver halide emulsion layers. Since my developing agent precursors are photographically compatible and stable in the light-sensitive photographic layers, elements containing them are as stable upon prolonged storage as are photographic elements containing no developing agent precursor. Photographic elements containing my' developing agent precursors are readily developed by treating the image exposed element with an activator solution.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that varitions and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A light-sensitive photographic element comprising a support coated with at least one hydrophilic colloid-silver halide layer and at least one hydrophilic colloid layer containing a photographically compatible inactive developing agent precursor having the formula:

wherein M represents a metal atom selected from the class consisting of the lead atom, the calcium atom, the cadmium atom, the barium atom, the nickel atom, the zinc atom, the cobalt atom, the antimony atom, the titanium atom, and the chromium atom; D represents a silver halide developing agent that is a water-soluble hydraquinone having a chelating group substituted on the carbon atom of the ring adjacent to a hydroxyl group, such that said silver halide is contiguousto said developing agent precursor; and n represents an integer of from 1 to 3.

2. A light-sensitive photographic element comprising a support coated with at least one hydrophilic colloidsilver halide layer and at least one hydrophilic colloid layer containing a photographically compatible inactive silver halide developing agent precursor contiguous to said silver halide, said precursor being a chelate of (1) a metal atom selected from the class consisting of the lead atom, the calcium atom, the cadmium atom, the barium atom, the nickel atom, the zinc atom, the cobalt atom, the antimony atom, the titanium atom and the chromium atom, and (2) as a silver halide developing agent a watersoluble hydroquinone having a chelating group selected from the class consisting of an amino group and an aminoalkyl group substituted on the carbon atom of the ring adjacent to a hydroxyl group.

3. A light-sensitive photographic element of claim 2 in which the photographically compatible inert silver halide developing agent precursor is a compound of a metal atom selected from the class consisting of a lead atom, the calcium atom, the cadmium atom, the barium atom, the nickel atom, the zinc atom, the cobalt atom, the antimony atom, the titanium atom, the chromium atom and a developer having the formula:

wherein X represents a group selected from the class consisting of an amino group, and an aminoalkyl group; R R and R each represents a group selected from the class consisting of the hydrogen atom, an alkyl group, an aryl group, and an amino group, such that the groups X, R R and R combined have no more than a total of eight carbon atoms per mole of developer.

4. A light-sensitive photographic element of claim 2 in which the said silver halide and said photographically compatible, inactive silver halide developing agent precursor are in the same hydrophilic colloid layer.

5. A light-sensitive photographic element comprising a support coated with atleast one hydrophilic colloid layer containing light-sensitive silver halide and the lead salt of 2,5-bis [N,N-di(,B-hydroxyethyl)aminomethyl1hydroquinone.

6. A light-sensitive photographic element comprising a support coated with at least one hydrophilic colloid-silver halide emulsion layer and at least one hydrophilic colloid layer containing a developing agent precursor, said precursor being t-he reaction product of (1) a hydroquinone developing agent and (2) a metal ion selected from the class consisting of the lead ion, the calcium ion, the cadmium ion, the barium ion, the nickel ion, and zinc ion,

the cobalt ion, the antimony ion, the titanium ion and the chromium ion, such that said precursor is photographically compatible with the said emulsion at the emulsion V coating pH and can be converted to the free developing agent by an activating solution containing an anion selected from the class consisting of SO SO CNS, 01-, Br, I, OH, P0 and CO capable of reacting with the metal ion from the said developing agent precursor to form a product which is less dissociated than the developing agent precursor.

7. A process for producing a photographic image corresponding to a latent image in a light-sensitive photographic element comprising a support coated with at least one hydrophilic colloid-silver halide emulsion layer and at least one hydrophi lic colloid layer containing a photographically compatible inactive silver halide developing agent precursor having the formula:

where M represents a metal selected from the class consisting of the lead atom, the calcium atom, the cadmium atom, the barium atom, the nickel atom, the zinc atom, the cobalt atom, the antimony atom, the titanium atom and the chromium atom; D represents a water-soluble hydroquinone silver halide developing agent having a chelating group selected from the class consisting of an amino group, and an aminoalky-l group, said chelating group being substituted on the carbon atom of the ring adjacent to a hydroxyl group, and n represents an integer of from 1 to 3, such that the said precursor is contiguous to said silver halide, said process comprising the step of treating the said element with an activator solution which contains at least one anion selected from the class consisting of CNS", Cl Br, I-, OI-T, P0 and CO which reacts with the metal ion from the said precursor to form a product which is less dissociated than the developing agent precursor causing the release of free silver halide developing agents, said activator solution having a pH that activitates the free developing agent released and causes it to convert said latent image into a silver image.

Reicrences Cited by the Examiner UNITED STATES PATENTS 3,218,164 11/1965 Green et al. 9629 FOREIGN PATENTS 559,465 8/ 1957 Belgium. 974,059 9/ 1960 Germany. 1,038,913 9/ 1958 Germany.

OTHER REFERENCES De Fero Chemical Abstracts, vol. 39, p. 4554 (1945).

Halmekoski, Chemical Abstracts, vol. 54, pp. 1151-2, (1960).

Melnikor et al., Chemical Abstracts, vol. 31, p. 4310 1937).

Shuttleworth, Chemical Abstracts, vol. 42, p. 8104 (1948).

NORMAN G. TORCHIN, Primary Examiner.

ABRAHAM H. WINKELSTEIN, Examiner.

I. T. BROWN, Assistant Examiner. 

1. A LIGHT-SENSITIVE PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT COATED WITH AT LEAST ONE HYDROPHILIC COLLOID-SILVER HALIDE LAYER AND AT LEAST ONE HYDROPHILIC COLLOID LAYER CONTAINING A PHOTOGRAPHICALLY COMPATIBLE INACTIVE DEVELOPING AGENT PRECURSOR HAVING THE FORMULA: 